The 3-1-1 rule is an international security standard enforced across Turkish Airlines flights and primary hubs like Istanbul Airport regarding liquids, gels, and aerosols carried in hand luggage. Under this protocol, travelers must pack all liquid substances in individual containers that do not exceed 100 milliliters (roughly 3.4 ounces) each. All of these small containers must fit comfortably inside a single, transparent, resealable one-liter plastic bag. Each passenger is strictly restricted to just one such transparent bag, which must be presented separately at security checkpoints. Items exceeding these thresholds or failing to fit inside the bag are subject to confiscation by airport security personnel.